Biphenyl derivatives and method of preparing them



j. L 1950 F ROSENTHAL 2,496,667

BIPHENYL DERIVATIVES AND METHOD 0F PREPARING THEM Filed Nov. 30, 1945 [MUM/vm cfa new@ wfg w mw -chu- CH2 INVENTOR.

osenfhal mrow/Ey Patented Jan. 3l, 1950 OFFICE BIPHENYL DERIVATIVES AND METHOD F PREPARING THEM Fritz Rosenthal, Crescent Park, Borough of neumawr, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application November 30, 1945, Serial No. 632,033

(Cl. E60-618) 1s claims. l

This invention relates to the preparation of 2,5,25'tetrahalogeno4,4-divinyl biphenyl. It also relates to the preparation of certain other biphenyl derivatives which are intermediates in the preparation of the above mentioned end product. y

It is an object of the invention to prepare the compound 2,5.25' tetrahalogeno 4,4' divinylbiphenyl.

Another object is to prepare 2.5,2'5'-tetra halogeno-lA'-diacetyl-biphenyl.

Still another object is to prepare 2.5,25' tetrahalogenc 4,4'di (AB-hydroxyethyl) biphenyl The accompanying drawing illustrates the steps of the process.

The preparations will be illustrated using as starting products the chlorine derivatives which are cheaper and easier to obtain on the market.

The starting material used for the preparation may be 2,5dichloro-aniline. By means of the Sandmeyer reaction, well known in the art, sodium nitrite and potassium iodide are reacted Example 1 To 8 parts by weight of 2,5-dichloro-1-idobenzene held at a temperature of 230 C. are added 5 g. of precipitated copper powder. Heating at 23o-240 C. is continued with stirring for about 30 minutes. The reaction chamber is then cooled and the contents filtered. The filtrate is extracted with toluene and is violet in color at this stage. After standing several hours a mass of needlelike crystals forms. This mass is ltered and dried. The crystals dissolve easily in hot ethyl alcohol and when recrystallized are pure white in color. After filtering, they are dried at 50 C. and have a melting point of 106 C. The yield is about 58 percent.

Next, pure 2,5,25'-tetrachloro-biphenyl is reacted in solution with acetyl chloride in the presence of aluminum chloride. Referring again to the accompanying diagram it is seen that this forms 2,5,2'5'tetrachloro-4,4'-diacetyl-biphenyl. The following is ia more detailed example of the preparation.

Example 2 with 2,5-dichloro-aniline to produce 2,5-dichlorophenyl are dissolved in ten times as much carbon disulde. To this are rst added parts of aluminum chloride and then about 40 parts of acetyl chloride with stirring. This evolves hydrogen chloride. The composition is then reiluxed at 56 C. for 6 hours. At the end of this time, the reaction products are poured over ice and hydrochloric acid and allowed to stand for several hours until a precipitate forms. This precipitate is ltered, washed, and dried. The precipitate is puried by dissolving in boiling isobutyl alcohol and activated carbon and then filtered. The product is obtained in white crystalline form in a yield of about 78 percent. This white precipitate is 2.5,2'5'tetrachloro4,4'-diacetyl-biphenyl and its preparation is not found in the literature. From the diacetyl compound, longer alkyl chain derivatives can be formed using the well known Grignard reaction. It is also possible to reduce the dialkyl compounds to the corresponding alcohols and react these alcohols with phthalic anhydride to get new resinous products. The preparation of 2,5,25'tetrachloro4,4' diacetyl-biphenyl from 2,5,2'5'tetrachloro-biphenyl could not have been predicted from similar reactions carried outvwith dichloro benzene since the attempt to treat the latter compound in the same vmanner gives no observed reaction.

From the 2.5.2'5'-tetrachloro4,4-diacetyl-bil phenyl there can be formed a secondary alcohol which is also unreported in the literature. The above named compound is reduced with aluminum isopropoxide which process results in lforming the corresponding secondary alcohol, 2,5,2'5' tetrachloro4,4'di( -hydroxyethyD -biphenyL A more detailed example of the preparation is found below.

Example 3 57 parts by weight of 4,4tetrachloro4,4diacetyl-biphenyl are added to 80 parts of a concentrated solution of aluminum isopropoxide and 100 parts of isopropyl alcohol and the mixture is heated on a glycerine bath at -100" C. Separation from the acetone which forms ln this reaction may be eifected by fractionating for about 7 hours. The remaining mixture is then transferred to another container and stirred with concentrated sodium hydroxide` for 30 hours lwhile heating at 90 C. The sodium hydroxide treated mixture is allowed to cool. The bulk of the 2,5,25 tetrachloro 4,4 di- (-hydroxyethyl) biphenyl crystallizes out in crude form. An additional yield of 2,5,2'5'-tetrachloro-iA-dli-(- hydroxyethyl) -biphenyl can be obtained by filtering the liquid from the crude 2,5,25'-tetrach1loro 4,4 dihydroxyethyl) -biphenyl, separating the isopropyl layer of the nitrate, and evaporating said layer to dryness. The secondary alcohol is obtained by redissoiving and recrystallizing. The product, which is 2,5,2'5-tetrachloro-4,4'- di-(-hydroxyethyl) -biphenyl has a melting point of 252 C. and the yield is about 62 percent.

Another new compound. 2,5,2'5tetrachloro 4,4diviny1biphenyl was next prepared from the 2,5,2'5' tetrachloro 4,4' di-(-hydroxyethyl) biphenyl. The latter compound was found to lose two molecules of water when heated in the presence of activated alumina.

Example 4 J A silica glass tube may serve as the reaction chamber for preparing 2,5,2'5'-tetrachloro4,4' divinyl-biphenyl.. In this tube is placed a combustion boat charged with 1 part by weight of 2,5,2'5'-tetrachloro-4,4'di (IB-hydroxyethyl) -biphenyl to 0.1 part hydroquinone which latter substance is used as a polymerization inhibitor. The tube also contains a layer of 2 parts oi activated alumina which serves as the dehydrating agent. The tube is strongly heated to 60G-800 C. and the dehydration reaction occurs in the vapor phase. Immediatly adjacent the reaction zone the vapor is rapidly chilled with cold water which causes the divinyl compound to condense and cool below a temperature favoring polymerization.

Example 5 The reaction is carried out as above but the pressure in the reaction tube is reduced to 5-10 mm. of mercury and the air is replaced by nitrogen or some other inert gas. A slow stream of the gas is used to sweep the vapors from the reaction zone to the cooling zone.

The 2,5,2'5tetrachloro4,4'-divinyl-biphenyl formed ln this process has a particularly valuable use in the prepartion of copolymers with long chain hydrocarbon resins of the kind typined by polystyrene. Copolymerization may also be carried out with other vinyl type resins.

Although hydroquinone is a preferred polymerization inhibitor, others may be used including benzoquinone, cresol, and pyrogallol. It is also possible to obtain results using no inhibitor but in that case the yield is not as satisfactory.

Dehydrating agents other than activated alumina may also be used. Some examples of these are anhydrous zinc chloride, anhydrous potassium hydroxide, thorium oxide, and tungsten oxide.

The dehydration reaction may be carried out in air either at atmospheric pressure or under reduced pressure. In general a high vacuum distillation produces better yields. Also favorable to high yields is the use of an inert atmosphere such as nitrogen, argon, or helium which may be preshydration reaction is carried out under reduced pressure and in an inert atmosphere.

4. The method of claim 1 in which the iinal dehydration reaction is carried out under reduced pressure and in anvatmosphere oi nitrogen.

5. The method oi claim 1 in which the nnal dehydration reaction is carried out in the presence of activated alumina. f

6. The method oi preparing 2,5,2'5'tetrahal geno-4.4'di(p-hydroxyethyl) -biphenyl comprising reacting 2,5.2'5'tetrahalogeno4,4'-diacetyl blphenyl with aluminum isopropoxide.

' 7. In a method of preparing 2,5,2'5'tetrahalo gem-4,4'-divinyl-biphenyl the step which includes dehydrating 2,5,2'5'tetrahalogeno-4.4'-di (-hydroxyethyl) biphenyl.

8. In a method of preparing 2,5,2'5'tetrahalo gene-4,4'-divinyl-biphenyl the steps which include strongly heating 2,5,25'-tetrahalogeno 4,4'di(hydroxyethyl)-biphenyl in the presence o! a dehydrating agent and immediately chilling the vaporized reaction products to `the solid state.

9. The method oi claim 8 in which the dehydrating agent is activated alumina.

10. The method of claim 8 in which a polymerization inhibitor is heated with the 2,5,2'5'- tetrahalogeno-4,4' -di- (p-hydroxyethyl) -biphenyL 11. The method of claim 8 in which hydroquinone is heatedwith 2,5,2'5'-tetrahalogeno 4,4di (-hydroxyethyl) -biphenyL 12. In a method of preparingl 2,5,2'5'tetra halogeno-4,4'-divinyl-hiphenyl the steps which include strongly heating 2,5,2'5'tetrahalogeno ent either at atmospheric pressure or reduced to l a pressure of about 10 mm. of mercury.

I claim as my invention:

1. The method of preparing 2,5,2'5'tetrahalo gene-4,4'-divinyl-biphenyl comprising reacting 2,5,2'5'-tetrahalogeno-biphenyl with acetyl chloride in the presence of aluminum chloride to form 2,5,25-tetrahalogeno-4,4'-diacetyl-biphenyl, reacting said 2,5,2'5'tetrahalogeno4,4'-diacetylbiphenyl with aluminum isopropoxide to form 2,5,2'5'-tetrahalogeno4,4'di (-hydroxyethyl) biphenyl, and reacting said 2,5,2'5tetrahalo geno-4,4'di(p-hydroxyethyl)-biphenyl in the presence of a dehydrating agent to form 2,5,2'5- tetraha1ogeno-4,4'-divinyl-biphenyl.

ence of a dehydrating agent and a polymerization inhibitor, and immediately chilling the vaporized reaction products to the solid state, said dehydrating reaction taking place under reduced pressure.

13. 'I'he process of claim 12 in which the dehydrating reaction is carried out in an inert atmosphere.

14. The process of claim 12 in which the dehydrating reaction is carried out in an atmosphere oi.' nitrogen.

15. The compound 2,5,2'5tetrahalogeno-4,4' di- (-hydroxyethyl) biphenyl.

divinyl-biphenyl.

FRITZ ROSEN'I'HAL.

REFERENCES CITED The following references are oi' record in the 111e of this patent:

UNITED STATES PATENTS Number Name Date 2,033,541 Ralston et al. Mar. 10, 1930 2,390,368 Hochwalt Dec. 4, 1945 2,427,337 Abbott et al Sept. 16, 1947 FOREIGN PATENTS Number Country Date 115,688 Australia Aug. 6, 1942 OTHER REFERENCES Ulmann, Liebigs Annalen de Chemie, voi. 332. pages 55-56 (1904).

Beilstein, Handbook of Organic Chemistry, vol.

5, 1st. supplement. page 273 (1931). 

1. THE METHOD OF PREPARING 2,5,2''5''-TETRAHALOGENO-4,4''-DIVINYL-BIPHENYL COMPRISING REACTING 2,5,2''5''-TETRAHALOGENO-BIPHENYL WITH ACETYL CHLORIDE IN THE PRESENCE OF ALUMINUM CHLORIDE TO FORM 2,5,2''5''-TETRAHALOGENO-4''4''-DIACETYL-BIPHENYL, REACTING SAID 2,5,2''5''-TETRAHALOGENO-4,4''-DIACETYLBIPHENYL WITH ALUMINUM ISOPROPOXIDE TO FORM 2,5,2''5''-TETRAHALOGENO-4,4''-DI-(B-HYDROXYETHYL)BIPHENYL, AND REACTING AND 2,5,2''5''-TETRAHALOGENO-4,4''-DI-(B-HYDROXYETHYL)-BIPHENYL IN THE 